Red tide is a type of harmful algae bloom (HAB) caused by an increase or “bloom” in the concentration of certain microscopic algae in the water column. Red tide events have been noted in Florida since the 1800’s and most certainly occurred prior to European settlement. The most common alga red tide in Florida is the dinoflagellate Karenia Brevis. In high enough concentrations the alga turns the water column a distinct red color.
The toxin produced by the alga can affect the central nervous system of fish and other marine life. Respiratory and skin irritations have been reported. Locally caught clams, oyster , scallops should not be consumed during a bloom, however shrimp, crabs and fish can be consumed during a red tide. There are numerous poorly understood factors that are associated with red tide which make it hard to determine when and with what severity a bloom will occur.